Im2

Im2 is the Colicin Immunity Protein for Colicin E2, produced by the cell at the same time to protect itself from the DNase Activity of the cytotoxic domain of ColE2. It is released when the Colicin binds to a cell surface receptor of a target cell.

Im2 is also capable of binding to Colicin E9, which has a high level of sequence homology to ColE2, and also inhibit the activity of the cytotoxic domain. This structure shows the binding of colicin E9 to Im2. 

3D structures of colicin-E2 immunitiy protein
Colicin Immunity Protein